With this distance, I think you have a few options.... The most affordable option is to use SmartMesh to form a mesh link by placing an AP near the windows / exterior walls of each building such that the AP's attempt to form a mesh link through the parking lot. Ruckus AP's have a a receive sensitivity that is 15+ dB better than the average wifi client, so it can pick up its own signal from much further away.
You can also use a sectorized/narrow antenna outdoor AP, such as the T301s or T301n, aimed from one building to the other. This AP puts out an ordinary wifi signal but it shoots the beam either in a narrow fan shape (T301s) or literally as a narrow rectangular beam (T301n) outwards, which dramatically improves distance reach compared to a traditional AP, which was meant to serve clients equally in all directions.
Sometimes a AP like this can directly provide wifi coverage into the building. Otherwise, you may need to combine this with SmartMesh and put another AP inside the remote office within reach of the T301, to adequately provide coverage within the building.
Finally, another option is the P300 or 7731 point-to-point bridge. These are pairs of specially adapted Ruckus AP's that basically function as an ethernet cable in the air. This might be overkill for your project, as the 7731/P300 can be used with kilometers of separation.
I would say the second option (T301s/T301n mesh to remote office AP) is the technically correct option / formal option that one would officially recommend. However, don't underestimate the effectiveness of the first approach especially if you're on a tight budget. I've covered some pretty large outdoor gaps before simply by placing an indoor AP near a externally facing wall/window.
